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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    
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<script>
    //创建数组并赋值
    let arr =[23,566,21,542,78];
    console.log(arr[2]);//21
    let arr2 = ['tom',34.4,true,,,,];
    console.log(arr2[4]);
    arr[4] = null;
    console.log(arr2[4]);

    console.log('---------');

    //遍历数组
    console.log(arr.length);//获取数组长度
    for (let i=0;i<arr.length;i++){
        console.log(arr[i]);
    }

    console.log('----------');

    //1.找出数组score中的最大值，并算出这个数组的平均数
    //score = [89,67,59,90,54,77,83,88,5,43,10,68];
    let score=[89,67,59,90,54,77,83,88,5,43,10,68];
    let max = score[0] ;
    let sum = 0;
    console.log(score.length);
    for (let i = 0;i<score.length;i++){
       if(score[i]>max){
        max =score[i];
       }
       sum += score[i];
    }
    let avg = sum /score.length;
    console.log('最大值是：'+max);
    console.log('平均数为：'+avg);
    score[1000] = 88;
    console.log(score[1000]);
    console.log(score.length);
    for (let i=0;i<score.length;i++){
        console.log(score[i]);
    }
    delete


</script>
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